The present invention relates to weed trimmers and, more particularly, to weed trimmer cutting heads.
Weed trimmers have gained popularity as a convenient device for cutting grass, weeds, and brush, especially in difficult access areas around home, businesses, and farms. A number of cutting heads for these devices have been disclosed to meet the needs of users. An example of such a device is disclosed in U.S. Pat. No. 5,640,836 by the applicant. The blade assembly for weed trimmers disclosed in this patent comprises pivoting steel blades for cutting heavy weeds, vines and underbrush as well as grass and lighter growth.
In many residential areas, string type weed trimmer heads utilizing a monofilament plastic string are popular due to the fact that the string cutting elements are less likely to cause damage to trees, shrubs, and fences if the cutting head is brought too near the trimmed object. These devices are often simpler and less costly than blade units.
One of the major disadvantages of the string type cutting heads is that the string is easily cut or damaged, especially if hard objects are inadvertently encountered. In these cases, the string must be frequently replaced, taking considerable time. In an effort to address this problem, a number of cutting heads have been introduced on the market which contain a spool of string. A number of methods are used to manually, or in some cases automatically, extend additional string when the old string becomes cut or damaged.
Theses units, while partially successful in addressing the problem of string replacement, have added bulk and weight, making use of the trimmer more difficult. Many smaller weed trimmers do not have the power or ruggedness to utilize these units. In many cases, these units fail to function as intended due to poor design, inadequate maintenance, or improper use. Changing string types or diameters is difficult and time consuming. Inventories of different string types is expensive due to the quantities of string used in the spools. These devices also are expensive to purchase and maintain.
So called "cut length" string trimmers, on the other hand, are simple, light and reliable to use. However, many require too much time for string replacement, especially when the head must be removed from the trimmer to replace the string.